When you bring a balloon (typically negatively charged due to rubbing it on hair or fabric) towards a wall, the charges in the wall respond due to electrostatic induction.
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Separation of Charges: The negative charges on the balloon repel the electrons in the wall's material, causing the electrons to move away from the side of the wall closest to the balloon. This results in an area of positive charge (due to a deficiency of electrons) forming on the wall near the balloon.
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Attraction: As a result of this charge separation, the wall now has a positive area that is attracted to the negatively charged balloon. This attraction can lead to the balloon sticking to the wall.
In summary, as the balloon approaches, the wall experiences a redistribution of charges, where positive charges are induced closer to the balloon, resulting in an attractive force.